Explain how primary and secondary active transport works, how they are related, and how they are different.

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enotechris | College Teacher | (Level 2) Senior Educator

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Active Transport is a process by which ions or molecules move against a concentration gradient; in other words, moving towards an area where there are already numbers of ions or molecules.  This process is the opposite of Diffusion, or Passive Transport, where they move from a concentrated area to a less concentrated area.  Diffusion takes no energy to perform, Active Transport, as the name implies, requires energy.

Primary Active Transport uses energy stored in the ATP molecule to drive a sodium/potassium "pump" which moves sodium ions out of a cell, and moves potassium ions into the cell.  The result is that there's a high concentration of potassium, and low concentration of sodium inside the cell.  The reverse is found outside the cell -- a high concentration of sodium, and a low concentration of potassium.

Secondary Active Transport does not use an ATP driven pump; instead, it employs carrier proteins to move the required ions or molecules across the cell membrane.



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